Transcript centre of gravity - Western Springs College

Year 11 Physical Education: Anatomy, Biomechanics & Physiology
YOU DO THE MATH!
Bones + Muscles + Movement = Life
1.
Movement
occurring at
the knee?
2. Movement
occurring at
the foot?
Answer the following –
NO TALKING
1. Movement at the Knee?
2. Agonist for movement 1?
3. Antagonist for movement
1?
4. Movement of the foot
(movement 2)?
5. Agonist for movement 2.
3.
Movement
occurring at
the
shoulder
6. Antagonist for movement
2?
7. Movement at the
shoulder (movement 3)
8. Agonist for movement 3?
9. Antagonist for movement
3?
Biomechanics Lingo
Page 129
Fill in “ What I think it means”
You have 10 minutes only!!!
If you don’t know something, have a go anyway
At the end of the unit we will come back and see how much you have learnt!!
BIOMECHANICS
Biomechanics is the study of forces and how
your body moves
What is a Force?
A force is a push or pull.
A force can cause….
a body at rest to move
a moving body to slow down
a moving body to stop
a change of direction
an increase in speed
MOTION
Any movement is called motion (general, linear and angular) When a body
changes its position relative to a fixed point it is said to be in motion.
LINEAR MOTION
a)
Occurs in a straight line by a person or object
b)
For example, jumping in the air to catch a ball, skiing
ANGULAR MOTION
a) Movement that occurs around an
axis
b) The axis can be internal (e.g. body
parts rotating around a joint – ice
skater pirouette, forward roll) OR
external (e.g. holding onto
something outside the body –
spinning a ball on your finger,
gymnast rotating round a
horizontal bar).
GENERAL MOTION
a)
A combination of linear and angular movement
b)
Most common of all movements (e.g. swimming – arms are rotating
around the shoulder and the rest of the body is moving in a line,
Cycling,
running).
LINGO
Mass : the amount of substance in a body (measure in kilograms)
Gravity: the pull of the earth
Force: a force is a push or a pull (measured in newtons)
External: outside, not from within the body
Stability: Maintaining balance, affected by COG, BOS & LOG
CENTRE OF GRAVITY
‘The centre point of a body’s mass.
The point at which all parts of an
object are equally balanced’
• For a normal human being standing
upright, their COG lies around the BELLY
BUTTON. This changes depending upon
what position the body is in.
• For example, if the hands are stretched
up in the air, the centre of mass will RISE
slightly because part of the body’s mass
has risen.
Where is our centre of gravity?
Its around our belly button
Would it be the same for girls and
guys?
Think about how girls weight is
distributed compared to boys
weight.
However, COG is not always found within
the body
Eg. if you bend forwards (abdominal flexion) your
COG moves forward
Eg. If you lift one of your arms up (abduction)
your COG moves up and out towards the side you
lifted.
Lowering your
COG will
increase your
stability.
E.g bending
your knees
BASE OF SUPPORT
‘Area within an objects point of contact with the ground’
• The LARGER the area the base of support covers, the more stable an
object will be.
• Pushing activity… volunteers
LINE OF GRAVITY
‘An imaginary vertical line that passes through the centre of gravity’
• Important when determining the stability of an object. If the LOG falls WITHIN the
objects base of support (BOS) the object is relatively stable
• If the LOG falls OUTSIDE the objects base of support, the object is relatively unstable
• Partner activity: standing against the wall
STABILITY SUMMARY
There are four points that you need to remember!!
A WIDE base of support will increase stability
If the line of gravity falls WITHIN the base of support, it will increase stability
A LOW centre of gravity will increase stability.
Lean into the oncoming force
QUICK QUIZ
Which type of motion would a pirouette in ice-skating be?
Freestyle swimming?
Toboganning down a hill?
List 3 ways a person can increase their stability
NEWTONS LAWS
Newton’s law of Inertia
Newton’s law of Acceleration
The law of action/reaction